This invention relates to deep water mining apparatus and to a jet pump for use with such apparatus, for collecting and recovering metal ore, etc., from, for example, the ocean floor.
Pieces of manganese and other metal ores ranging in size from 0.5 to 25 cm in diameter lay scattered across the ocean floor at depths of up to 5,000 to 6,000 meters. A mining apparatus for collecting these pieces and bringing them up to the surface should be as uncomplicated as possible and at the same time be capable of providing efficient mining performance. In addition, concerning a jet pump in the form described in U.S. Pat. No. 4,487,553, the design of such a pump calls for the main body of the pump to be formed in the shape of a conical shell, with pressurized water being jetted from a large number of nozzles arranged around the circumference of the large-diameter end (base) of this shell. High-pressure air is sprayed in the vicinity of these nozzles in order to enclose the pressurized water jets with air and thus prevent the occurrence of vortex kinetic energy.
However, although this jet pump design works well when the pressure of the water jets from the nozzles is relatively low and the flow volume is large, problems occur when high-pressure jets are used in order to improve the overall performance of the pump. Experiments show that the cause of these problems is that the cross-sectional area (or diameter) of the jets is inversely proportional to the flow speed of the jets and decreases as the speed of the jets increases, thus causing gaps to appear between adjacent water jets. These gaps are not filled by the air being introduced, and consequently a current flow in the opposite direction of the jets is created in these gaps. As a result of this reverse current, the jets and the layers of air enclosing them are disturbed, thus causing a reduction in performance efficiency.
It is a general object of this invention to provide mining apparatus which is uncomplicated in design and which provides for efficient recovery of metal ore and other minerals, and which also uses an improved jet pump.